Process for the activation of a copper-, zinc- and zirconium oxide-comprising adsorption composition

ABSTRACT

A process for the activation of a copper, zinc and zirconium oxide-comprising adsorption composition for the adsorptive removal of carbon monoxide from substance streams comprising carbon monoxide and at least one olefin wherein: (i) in a first activation step an activation gas mixture comprising the olefin and an inert gas is passed through the adsorption composition; and (ii) in a second activation step the adsorption composition is heated to a temperature in the range from 180 to 300° C. and an inert gas is passed through it, wherein the steps (i) and (ii) can each be performed several times.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. patent application Ser. No.13/228,309, filed Sep. 8, 2011, now U.S. Pat. No. 8,637,723, whichclaims the benefit of U.S. Provisional Application Ser. No. 61/381,081filed Sep. 9, 2010, the entire contents of which are incorporated hereinby reference in their entirety.

BACKGROUND OF THE INVENTION

The invention relates to a process for the activation of a copper, zincand zirconium oxide-comprising adsorption composition for the adsorptiveremoval of carbon monoxide from carbon monoxide-comprising substancestreams and a process for the removal of carbon monoxide from carbonmonoxide-comprising substance streams comprising the activation of theadsorption composition.

In various sectors of industry, it is important to have especially puresubstance streams available. Catalytic chemical reactions are oneexample. Catalysts are often very sensitive to poisoning. Thus, evenexceptionally small quantities of impurities in the starting materialstream can collect on the catalyst and poison it. Typically, for olefinpolymerization reactions on modern catalysts, for example metallocenecatalysts, olefin streams are required which comprise not more than afew ppb (parts per billion, i.e. 10⁻⁹ parts) of impurities per part ofthe desired substance (“polymer-grade” olefins). Olefins deriving fromtypical olefin sources (steam cracker, fluid catalytic cracker,dehydrations, MTO (“methanol to olefins”) processes mostly have verymuch higher contents (ppm or even per-mille range) of impurities such ascarbon monoxide or oxygen (“chemical grade”); these contents must bedecreased appropriately before use for polymerization.

Typically, the substance streams to be purified are air, nitrogen orargon or hydrocarbons such as ethylene, propylene, 1-butene, 2-butene,1,3-butadiene or styrene. Typical impurities which must as a rule beremoved are oxygen and carbon monoxide, and often also water, carbondioxide, hydrogen or even sulfur, arsenic or antimony compounds.Processes for the removal of such impurities from substance streams areknown.

Many adsorptive processes and adsorbents for the removal of carbonmonoxide from substance streams are known. The German laid-openspecification DE 1 929 977 teaches catalysts comprising 20 to 60 partsof CuO to 100 parts of ZnO and the use thereof for the removal of COfrom ethylene and propylene streams at a temperature in the range from50 to 200° C. U.S. Pat. No. 3,676,516 teaches a supported Cu catalyst,whereof 20 to 95% of the copper is present as Cu²⁺, and the use thereoffor CO removal from ethylene or propylene streams at a temperature belowabout 200° C., and in the examples specifically at about 93° C. U.S.Pat. No. 4,917,711 discloses an adsorbent which comprises a coppercompound on a high-surface-area support, but also adsorbs olefins andhence is only suitable for the purification of nitrogen, inert gases andsaturated hydrocarbons.

WO 95/021146 A1 teaches a process for the removal of carbon monoxide andalso arsine, if present, from liquid hydrocarbon streams by contactingwith a sorbent which, depending on the embodiment, comprises dispersedcopper at the oxidation levels 0, +1 or +2, and in certain cases alsomanganese dioxide. EP 537 628 A1 discloses a process for the removal ofcarbon monoxide from alpha olefins and saturated hydrocarbons bycontacting with a catalyst system based on at least one oxide of a metalselected from Cu, Fe, Ni, Co, Pt and Pd and at least one oxide of ametal selected from groups 5, 6 or 7 of the periodic table of theelements at 0 to 150° C. U.S. Pat. No. 4,713,090 describes an adsorbentfor obtaining high-purity carbon monoxide by pressure or temperatureswing adsorption. The adsorbent comprises a composite support with acore of silicon or aluminum oxide and an outer layer of an activatedcharcoal on which a copper compound is supported.

WO 2004/022223 A2 teaches a copper-, zinc-, zirconium- and optionallyaluminum-comprising adsorption composition and the use thereof for theremoval of CO from substance streams in the completely reduced state.

Processes are also known for activating or reactivating catalysts, alsothose comprising copper, or passivating them for transport. DD 0 153 761relates to a process for the activation or reactivation of ironmolybdate redox catalysts, which can also comprise copper, wherein thecatalysts are first calcined in a non-oxidizing atmosphere and thenbrought into contact with an oxidizing gas. DE 199 63 441 A1 teaches aprocess for the regeneration of copper-comprising hydrogenationcatalysts by first oxidizing and then reducing treatment, wherein thereduction is preferably first performed in the hydrogenation reactor. WO02/068 119 A1 discloses copper-comprising hydrogenation anddehydrogenation catalysts which are used in the reduced state and arepassivated for transport by partial oxidation of the copper. EP 296 734A1 describes copper-comprising shift or methanol catalysts which owingto reduction at a temperature below 250° C. have a Cu surface area of atleast 70 m²/g based on copper.

WO 2007/093526 discloses a copper, zinc and zirconium oxide-comprisingadsorption composition, where the copper-comprising fraction thereof hasa reduction level, expressed as the weight ratio of metallic copper tothe sum of metallic copper and copper oxides, calculated as CuO, of atleast 45% and at most 75%, and a process for the removal of carbonmonoxide from carbon monoxide-comprising substance streams by adsorptionon this adsorption composition. An adsorption composition with areduction level in the stated range is supposed to be especiallyregenerable.

WO 2007/093526 also discloses a process for the production of theadsorption composition by:

-   -   a) preparation of a solution of the components of the adsorption        composition and/or of soluble starting compounds for these;    -   b) precipitation of a solid from this solution by addition of a        base;    -   c) separation and drying of the solid;    -   d) optionally a calcination of the solid;    -   e) shaping of the solid into shaped bodies; and    -   f) optionally a calcination of the shaped bodies;    -   g) adjustment of the reduction level of the copper-comprising        fraction of the adsorption composition to a value of at least        45% and at most 75%.

During this after the complete reduction with hydrogen, the reductionlevel is adjusted to the desired value by oxidation of the adsorptioncomposition precursor. During this, the residual hydrogen present isflushed from the reaction vessel with nitrogen, the desired oxidationtemperature is set and a small proportion of oxygen is mixed into thenitrogen stream.

Depending on the selected adsorber size, the maximum uptake capacity ofthe adsorption composition for carbon monoxide comprised therein issooner or later reached, so that it must be regenerated.

WO 2007/093526 also discloses the regeneration of the copper, zinc andzirconium oxide-comprising adsorption composition after the use thereoffor the adsorptive removal of carbon monoxide from carbonmonoxide-comprising substance streams by passing an inert gas such asfor example nitrogen, methane or argon over the adsorption compositionat a temperature of preferably at least 150° C. and at most 400° C. WO2007/093526 also discloses the addition of oxygen in traces, in generalin a proportion of at least 1 ppm, preferably at least 5 ppm andparticularly preferably at least 10 ppm, in general at most 300 ppm,preferably at most 250 ppm and particularly preferably 200 ppm to theinert gas, preferably nitrogen or argon.

During the regeneration, the reduction level of the copper-comprisingfraction of the adsorption composition can increase. However, at veryhigh reduction levels, for example of 85%, a further rise in thereduction level can lead to an abrupt fall in the uptake capacity of theadsorption composition for CO. Particularly with multiple regenerationthe danger exists that a certain critical reduction level will beexceeded and the uptake capacity of the adsorption composition falls.

An excessively low reduction level also has an adverse effect on theuptake capacity of the adsorption compositions for carbon monoxide. At areduction level of <50%, the uptake capacity is already markedly loweredand is now only ca. 40% of the uptake capacity at a reduction level of70%.

BRIEF SUMMARY OF THE INVENTION

The objective of the invention is to provide an improved process for theregeneration of a copper, zinc and zirconium oxide-comprising adsorptioncomposition after the use thereof for the adsorptive removal of carbonmonoxide from substance streams comprising carbon monoxide and olefins.In particular the objective of the invention is to provide an improvedprocess for the removal of carbon monoxide from substance streamscomprising carbon monoxide and at least one olefin, wherein the uptakecapacity of the adsorption material lies in an optimal range.

The problem is solved by a process for the activation of a copper, zincand zirconium oxide-comprising adsorption composition for the adsorptiveremoval of carbon monoxide from substance streams comprising carbonmonoxide and at least one olefin, wherein

-   -   (i) in a first activation step an activation gas mixture        comprising the olefin and an inert gas is passed through the        adsorption composition, and    -   (ii) in a second activation step the adsorption composition is        heated to a temperature in the range from 180 to 300° C. and an        inert gas is passed through it,    -   wherein the steps (i) and (ii) can each be performed several        times.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a chart showing the CO uptake capacity of the adsorptioncomposition as a function of the reduction level R.

FIG. 2 presents the results of the experiments with an adsorptioncomposition with an initial reduction level of 77%.

FIG. 3 presents the results of the regeneration of an adsorptioncomposition with an initial reduction level of 67% with industrialnitrogen at 250° C.

FIG. 4 shows the results of experiments in which regeneration steps 1 to4 were performed with pure N₂ at 250° C. and the regeneration steps 5 to9 at 200° C. with nitrogen comprising 1500 ppm O₂.

DETAILED DESCRIPTION OF THE INVENTION

It was found that during the treatment of the adsorption composition inan inert gas stream at a temperature in the range from 180 to 300° C.the reduction level of the copper-comprising fraction of the adsorptioncomposition increases if an olefin was previously adsorbed onto theadsorption composition. Olefins adsorbed onto the adsorption compositionpresumably act as reducing agents here and are themselves oxidized tocarbon dioxide and water by oxygen bound in the adsorption composition.During this, copper(I) and/or copper(II) comprised in the adsorptioncomposition is reduced to copper or copper(I).

XPS measurements have moreover shown that the freshly prepared catalystis coated with a thin passivating layer of CuO and Cu(OH)₂. By treatmentwith pure inert gas without addition of oxygen, CuO and Cu(OH)₂ in thepassivating layer are reduced to Cu₂O by adsorbed olefin and theadsorption composition is thereby activated. As a result of this, the COuptake capacity climbs considerably.

Thus, before the first adsorption step for the removal of CO fromolefin, generally liquid, the adsorption composition is activated inthat in a first treatment step (i) an activation gas stream whichcomprises the gaseous olefin, preferably gaseous propylene, is passedthrough it and then in a second step (ii) pure inert gas, in generalnitrogen, is passed through it.

The activation gas stream used in step (i) in general comprises 1 to 100vol. %, prefer-ably 5 to 75 vol. %, in particular 10 to 50 vol. % of theolefin. In the first treatment step (i), the GHSV is in general 100 to5,000 hrs⁻¹, preferably 200 to 1,000 hrs⁻¹, the treatment time is ingeneral 0.5 to 10 hrs, preferably 1 to 5 hrs, and the temperature of theadsorption composition is in general 0 to 100° C., preferably 15 to 50°C.

In the treatment step (ii) that follows, the adsorption composition isheated to a temperature in the range from 180 to 300° C., preferably 190to 270° C., in particular 200 to 250° C. and the pure inert gas ispassed through the adsorption composition. In this regeneration step,the GHSV is in general at least 100 hrs⁻¹, preferably at least 200hrs⁻¹. It is in general at most 5,000 hrs⁻¹, preferably at most 1,000h⁻¹. Here the treatment time is in general 0.5 to 24 hrs, preferably 1to 10 hrs.

The pressure during the activation is in general 0.5 to 5 bar,preferably 1 to 3 bar.

The steps (i) and (ii) can also be performed several times. In general,they are each performed alternately 1 to 10 times, for example 2 to 4times.

The activation comprising the steps (i) and (ii) is preferably performedwhen the copper-comprising fraction of the adsorption compositionexhibits a reduction level of less than 65%. In particular, it isperformed when the reduction level is less than 50%. Even an adsorptioncomposition with a reduction level of the copper-comprising fraction of0%, i.e. an adsorption composition which comprises copper exclusively inthe form of Cu(II), can be regenerated in this manner.

Preferably the copper-comprising fraction of the adsorption compositionexhibits a reduction level of at least 65% and at most 75% after theactivation has been performed.

The reduction level is a measure of the oxide content of the coppercomprised in the adsorption composition according to the invention. Thereduction level is determined as the weighted substance content ratio ofreduced copper, i.e. copper in the oxidation state 0 (Cu⁰) or 1 (Cu¹) tothe total copper, according to the formula:

${{Reduction}\mspace{14mu}{level}} = \frac{{{n({CuO})} \cdot 0} + {{n\left( {{Cu}_{2}O} \right)} \cdot 0.5} + {{n\left( {Cu}^{0} \right)} \cdot 1}}{{n({CuO})} + {n\left( {{Cu}_{2}O} \right)} + {n\left( {Cu}^{0} \right)}}$

where n means the substance content in mole.

Pure metallic copper would have a reduction level of 100%, pure CuO areduction level of 0%, and pure Cu₂O a reduction level of 50%. However,a certain reduction level does not necessarily mean that the adsorptioncomposition according to the invention comprises metallic copper or CuO.A certain reduction level can result through any possible composition ofappropriate proportions of metallic copper, Cu⁰, Cu₂O or CuO.

The reduction level is determined by any procedure that is capable ofquantitatively determining copper at its various oxidation levels.Particularly simple however is the complete oxidation of the copper in asample of the adsorption composition by contacting with air at atemperature of at least 250° C. and at most 500° C. until constantweight, which is normally reached after at least 10 minutes and at most12 hours. The reduction level of the sample is calculated from theweight gain of the sample under the assumption that additional weight isexclusively oxygen and assuming the following stoichiometry for theoxidation:2Cu+O₂→2 CuOor2Cu₂O+O₂→4 CuO

The following then applies:

${{{Reduction}\mspace{14mu}{level}} = {\frac{100}{\frac{M_{Cu} \cdot y_{CuO}}{M_{CuO} \cdot 100} - \frac{y_{CuO}}{100}} \cdot \left\lbrack {\frac{1}{\frac{\Delta\; m}{100} + 1} - 1} \right\rbrack}},$wherein

-   -   M is the molar mass of the relevant component Cu or CuO,    -   y_(CuO) is the mass proportion of CuO based on the sum of the        oxides of the completely oxidized catalyst, and    -   Δm is the relative mass gain in % due to total oxidation.

The reduction level of the activated adsorption composition is ingeneral at least 60%, preferably at least 65% and in general at most80%, preferably at most 75%.

Also a subject of the invention is a process for the removal of carbonmonoxide from substance streams comprising carbon monoxide and at leastone olefin by adsorption on a copper, zinc and zirconiumoxide-comprising adsorption composition comprising activation steps,adsorption steps and regeneration steps, wherein for the activation

-   -   (i) in a first activation step an activation gas mixture        comprising the olefin and an inert gas is passed through the        adsorption composition, and    -   (ii) in a second activation step the adsorption composition is        heated to a temperature in the range from 180 to 300° C. and an        inert gas is passed through it,        wherein the steps (i) and (ii) can each be performed several        times, in the adsorption steps the adsorption composition is        contacted with the substance stream comprising carbon monoxide,        and in the regeneration steps the adsorption composition is        heated to a temperature in the range from 180 to 300° C. and a        regeneration gas is passed through it, and the regeneration gas        comprises 1000 to 3000 ppm of oxygen in an inert carrier gas.

It was found that during the regeneration of the adsorption compositionin an inert gas stream the reduction level of the copper-comprisingfraction of the adsorption composition increases. Presumably during thedesorption process carbon monoxide is oxidized to carbon dioxide,whereby at the same time copper(I) and/or copper(II) comprised in theadsorption composition is correspondingly reduced. In addition, olefinsadsorbed on the adsorption composition which derive from the substancestream to be purified from CO presumably likewise act as reducingagents, during which they themselves are presumably oxidized to carbondioxide and water.

Through the presence of 1000 to 3000 ppm, preferably 1000 to 1900 ppm ofoxygen in the regeneration gas, the reduction of copper in theadsorption composition is counteracted, in that a moderate reoxidationof copper reduced by CO and/or olefin takes place. It was found thatwith a concentration of 1000 to 3000 ppm of oxygen, the reduction levelduring the regeneration process changes only slightly or even remainsessentially unchanged. Particularly good results are achieved with anoxygen content of 1300 to 1500 ppm. Naturally a particularly preferredinert gas is nitrogen, but other carrier gases chemically inert towardsthe adsorption composition are also possible, for example argon.

In the regeneration step, the GHSV is in general at least 100 hrs⁻¹,preferably at least 200 hrs⁻¹. It is in general at most 5,000 hrs⁻¹,preferably at most 1,000 hrs⁻¹. With an adsorption composition of thecomposition 70 wt. % CuO, 20 wt. % ZnO and 10 wt. % ZrO₂ and with adensity of 1.35, the oxygen quantity used in the regeneration step isfor example 2.3±0.5 normal liters per liter of catalyst. The oxygenquantity based on the catalyst mass is then for example 1.7±0.35 normalliters per kilogram of catalyst.

The duration of the regeneration is in general at least 1 hour,preferably at least 10 hours and particularly preferably at least 15hours, and in general at most 100 hours, preferably at most 50 hours andparticularly preferably at most 30 hours.

The adsorption composition activated and regenerated according to theinvention is well suited for the purification of substance streamscomprising one or more olefins. These are in general used in liquidform. Normal olefins which are freed from CO with the adsorptioncompositions used and regenerated according to the invention are ethene,propylene, 1-butene, 2-butene, 1,3-butadiene and/or styrene. Theadsorption composition is particularly suitable for the removal ofcarbon monoxide (CO) from liquid propylene.

Before implementation of the adsorption steps and after implementationof the regeneration steps, the regeneration composition according to theinvention preferably exhibits a reduction level of the copper-comprisingfraction of 60 to 80%. The reduction level should not exceed 90%,preferably 85%.

In particular, the reduction level of the copper-comprising fraction is65 to 75%. The adsorption composition admittedly does not then exhibitthe maximal adsorption capacity of such compositions for CO, but it isconsiderably more regenerable than compositions with a higher reductionlevel and higher CO uptake capability. In particular, in this range thedanger that a certain critical reduction level will be exceeded by theregeneration and that the uptake capacity for CO decreases markedly isvery slight. It is thus also outstandingly suitable for freeingsubstance streams with greatly fluctuating CO content from CO in plantswith two adsorbers, whereof at a given time one is being used for theadsorption and one is being regenerated.

The adsorption composition used according to the invention comprisescopper, zinc and zirconium oxides. Copper can also partly be present asmetallic copper and otherwise is present in the form of Cu(I) and Cu(II)oxides. In the pure form, the adsorption composition according to theinvention in general comprises copper in a quantity which calculated asCuO corresponds to at least 30 wt. %, preferably at least 50 wt. %, andparticularly preferably at least 60 wt. %, and in general at most 99.8wt. %, preferably at most 90 wt. % and particularly preferably at most80 wt. % of copper oxide CuO, each based on the total quantity of theadsorption composition. In the pure form, the adsorption compositionaccording to the invention in general comprises zinc oxide ZnO in aquantity of at least 0.1 wt. %, preferably at least 5 wt. %, andparticularly preferably at least 10 wt. %, and in general at most 69.9wt. %, preferably at most 40 wt. % and particularly preferably at most30 wt. %, each based on the total quantity of the adsorptioncomposition. Further, in the pure form, it in general compriseszirconium oxide ZrO₂ in a quantity of at least 0.1 wt. %, preferably atleast 3 wt. %, and particularly preferably at least 5 wt. %, and ingeneral at most 69.9 wt. %, preferably at most 30 wt. % and particularlypreferably at most 20 wt. %, each based on the total quantity of theadsorption composition. The zirconium dioxide fraction in the adsorptioncomposition can be partially replaced by aluminum oxide Al₂O₃. Forexample at least 1%, at least 10% or at least 30% and at most 90%, atmost 80% or at most 70% of the zirconium oxide fraction in theadsorption composition can be replaced by aluminum oxide. In the contextof this invention, “pure form” means that apart from the copper (oxide),zinc oxide and zirconium oxide (this optionally partially replaced byaluminum oxide) fractions, no other components are comprised, apart frominsignificant components which are for example entrained from thefabrication, such as residues of starting substances and reagents,additives for shaping and the like. “Pure form” thus means that theadsorption composition consists of the stated components.

The percentage contents of the adsorption composition always add up to100 wt. %.

A very suitable adsorption composition consists in the pure form of65-75 wt. % CuO, 15 to 25 wt. % ZnO and 5 to 15 wt. % ZrO₂, for exampleof ca. 70 wt. % CuO, ca. 20 wt. % ZnO and ca. 10 wt. % ZrO₂, and theproportions thereof add up to 100 wt. %.

The adsorption composition used according to the invention can be, butdoes not absolutely have to be, present in the pure form. It is possibleto mix it with additives or to apply it onto an inert support. Suitableinert supports are the known catalyst supports such as for examplealuminum oxide, silicon dioxide, zirconium dioxide, alumosilicates,clays, zeolites, diatomaceous earth and the like.

The adsorption composition used according to the invention is producedlike known oxide catalysts. A convenient and preferred process for theproduction of the adsorption composition used according to the inventioncomprises the following process steps in the stated order:

-   -   a) preparation of a solution of the components of the absorption        composition and/or of soluble starting compounds for these;    -   b) precipitation of a solid from this solution by addition of a        base;    -   c) separation and drying of the solid;    -   d) optionally a calcination of the solid;    -   e) shaping of the solid into shaped bodies;    -   f) optionally a calcination of the shaped bodies;        with the proviso that at least one of the two calcination        steps d) or f) is performed, and after or simultaneously with        step f) there is performed step    -   g) adjustment of the reduction level of the copper-comprising        fraction of the adsorption composition, expressed as the weight        ratio of metallic copper to the sum of metallic copper and        copper oxides, calculated as CuO, to a value of at least 60% and        at most 80%.

In the first process step, step a), a solution of the components of theadsorption composition is prepared in the usual way, for example bydissolution in an acid such as nitric acid. Optionally, instead of thecomponents of the adsorption composition, the starting materials forthese, for example the nitrates, carbonates or hydroxy-carbonates of themetals are dissolved in an aqueous solution, which can also be acidic,for example comprise nitric acid. The quantity ratio of the salts in thesolutions is calculated stoichiometrically and adjusted according to thedesired final composition of the adsorption composition.

In step b) a solid is precipitated from this solution as the precursorof the adsorption composition. This is effected in the usual way,preferably by increasing the pH of the solution by addition of a base,for example by addition of sodium hydroxide solution or soda solution.

Before the drying in step c), the solid precipitation product formed isas a rule separated from the supernatant solution, for example byfiltration or decantation, and washed free of soluble components, suchas sodium nitrate, with water. Before the further processing, theprecipitation product is then normally dried by normal drying methods.In general a treatment at slightly elevated temperature suffices forthis, for example at least 80° C., preferably at least 100° C. andparticularly preferably at least 120° C., over a period from 10 min to12 hours, preferably 20 min to 6 hours and particularly preferably from30 min to 2 hours. It is also possible and particularly convenient toconvert the product of the precipitation by spray-drying to a dry powderwhich can be further processed, either directly—a certain alkali, forexample sodium, content in the adsorption composition does not ingeneral interfere—or after washing.

Following the drying, the precipitated and dried adsorption compositionpreproduct is optionally subjected to the calcination step d). Thecalcination temperature used for this is in general at least 250° C.,preferably at least 300° C. and particularly prefer-ably at least 350°C., and in general at most 500° C., preferably at most 450° C. andparticularly preferably at most 410° C. The calcination time is ingeneral at least 10 minutes, preferably at least 20 minutes andparticularly preferably at least 30 minutes and in general at most 12hours, preferably at most 6 hours and particularly preferably at most 4hours. The drying step c) and the calcination step d) can merge directlyone into to the other.

After the drying step c) or the calcination step d), the adsorptioncomposition or precursor thereof is processed in the shaping step e)with normal shaping processes such as extrusion, tabletting or pelletinginto shaped bodies such as extrudates, tablets or—alsospherical—pellets.

After the shaping step, the adsorption composition or precursor thereofis optionally subjected to a calcination step f). The calcinationconditions to be used in step f) are identical with those of thecalcination step d).

In the course of its production, the adsorption composition is subjectedto at least one of the two calcination steps d) or f), and alsooptionally both. In the calcination step or steps, the adsorptioncomposition precursor is converted into the actual adsorptioncomposition and as usual the BET surface area and the pore volume of theadsorption composition inter alia are also established, during which, asis known, the BET surface area and the pore volume decrease withincreasing calcination time and calcination temperature.

Preferably calcination is performed at least long enough overall for thecarbonate content (calculated as CO₃ ²⁻) of the adsorption compositionto be at most 10 wt. %, based on the total weight of the calcinationproduct, and its BET surface area to have a value in the range from atleast 40 to at most 100 m²/g. The pore volume of the adsorptioncomposition, measured as water uptake, is adjusted to a value of atleast 0.05 ml/g during the calcination. These values are preferred forthe adsorption composition according to the invention.

The adsorption composition used according to the invention can also, asaforesaid, be deposited on a support. This is effected by normalimpregnation processes or deposition precipitation processes. As isknown, a deposition precipitation process is a precipitation process inthe presence of a support or a support precursor. To effect a depositionprecipitation process, in the precipitation process described above asupport or support precursor is preferably added to the solutionprepared in step a). If the support is already in the form of preshapedfinished shaped bodies, i.e. a pure impregnation process, the shapingstep e) is omitted, otherwise the support is also shaped in the courseof the processing of the adsorption composition preproduct byprecipitation, drying, calcination and shaping.

A preferred impregnation process for the production of the adsorptioncomposition according to the invention is performed with preshapedsupports and comprises the following process steps in the stated order:

-   -   a) production of a solution of the components of the absorption        composition and/or of soluble starting compounds for these;    -   b) impregnation of a preshaped support with this solution;    -   c) drying of the impregnated support; and    -   d) calcination of the impregnated and dried support,        wherein after or simultaneously with step d) there is performed        step    -   e) adjustment of the reduction level of the copper-comprising        fraction of the adsorption composition, expressed as the weight        ratio of metallic copper to the sum of metallic copper and        copper oxides, calculated as CuO, to a value of at least 60% and        at most 80%.

Process step a) of this impregnation process is performed like the stepa) of the precipitation process described above. In step b), a preshapedsupport is impregnated with the solution. The preshaped support has ashape corresponding to the use purpose, for example extrudates, tabletsor—also spherical—pellets. The impregnation is performed either withexcess solution or with the quantity of solution corresponding to thepore volume of the support (“incipient wetness”). After theimpregnation, the impregnated support is dried and calcined in steps c)and d) like the precipitation product in the precipitation process.However, with a preshaped support the shaping step is omitted.

Both in a precipitation and also in an impregnation process, a step foradjustment of the reduction level of the copper is necessary. This canbe effected by establishment of suitable process conditions in thecalcination (in particular calcination under an atmosphere notcompletely oxidizing copper) or in a separate process step after thecalcination, where in the latter case the adjustment of the reductionlevel does not necessarily have to take place directly after thecalcination. The adjustment of the reduction level is effected with anyknown process which is suitable for modifying the oxidation level ofcopper. If copper is mainly present in reduced form, it is reacted withoxygen, and with hydrogen if copper is mainly present in oxidized form.

Mostly, the calcination is performed under air, and consequently copperis present in the form of CuO in the precursor of the adsorptioncomposition according to the invention obtained after the calcination.The reduction level is then adjusted by reduction of the copper to thedesired reduction level. This is effected by treatment of the precursorpresent after the calcination with a reducing agent. Any reducing agentcapable of reducing copper can be used. The exact reduction conditionsto be used are dependent on the precursor and the composition thereofand on the reducing agent used and can easily be determined in a fewroutine experiments. A preferred process is treatment of the precursorwith hydrogen, mostly by passing a hydrogen-comprising gas, preferably ahydrogen/nitrogen mixture, over it at elevated temperature.

It is also possible firstly to reduce the precursor of the adsorptioncomposition used according to the invention completely and then tooxidize it to the desired reduction level. The complete reduction of theprecursor of the adsorption composition is effected by reduction of thecopper comprised in the adsorption composition to copper metal. This canin principle be effected with any reducing agent which can reduce thecopper from the oxidation states I or II to oxidation state 0. This canbe effected with liquid or dissolved reducing agents, and in this casedrying is necessary after the reduction. Hence reduction with a gaseousreducing agent is very much more convenient, above all reduction withhydrogen by passing a hydrogen-comprising gas over it. The temperatureto be used in this is in general at least 100° C., preferably at least140° C. and particularly preferably at least 160° C. and in general atmost 250° C., preferably at most 220° C. and particularly preferably atmost 200° C. A suitable temperature is for example ca. 180° C. Thereduction is exothermic. The quantity of reducing agent added should beadjusted so as not to depart from the selected temperature window. Theprogress of the activation can be followed on the basis of thetemperature measured in the adsorption agent bed(“temperature-programmed reduction, TPR”).

A preferred method for the reduction of the adsorption compositionprecursor is to establish the desired reduction temperature after adrying performed under a nitrogen stream and to add a small proportionof hydrogen to the nitrogen stream. For example a suitable gas mixtureinitially comprises at least 0.1 vol. % hydrogen in nitrogen, preferablyat least 0.5 vol. % and particularly preferably at least 1 vol. %, andat most 10 vol. %, preferably at most 8 vol. % and particularlypreferably at most 5 vol. %. A suitable value is for example 2 vol. %.This initial concentration is either maintained or increased, in orderto reach and maintain the desired temperature window. The reduction iscomplete when in spite of constant or increasing levels of the reducingagent the temperature in the composition bed decreases or hardly anymore water of reduction is formed. A typical reaction time is in generalat least 1 hour, preferably at least 10 hours and in general at most 100hours, preferably at most 50 hours.

The drying of the precursor of the adsorption composition, if necessary,is effected by heating the precursor to a temperature of in general atleast 100° C., preferably at least 150° C. and particularly preferablyat least 180° C. and in general at most 300° C., preferably at most 250°C. and particularly preferably at most 220° C. A suitable dryingtemperature is for example ca. 200° C. The precursor is kept at thedrying temperature until only no longer interfering residues of adheringmoisture are still present; this is in general the case after a dryingtime of at least 10 minutes, preferably at least 30 minutes andparticularly preferably at least 1 hour and in general at most 100hours, preferably at most 10 hours and particularly preferably at most 4hours. The drying is preferably effected in a gas stream in order totransport the moisture out of the bed. Dry air can for example be usedfor this, however it is particularly preferable to pass an inert gasthrough the bed, and nitrogen or argon are particularly suitable here.

After the complete reduction, the reduction level is adjusted to thedesired value by oxidation of the adsorption composition precursor. Thiscan be effected with any known oxidizing agent capable of oxidizingcopper. Oxygen is conveniently used for this, in particular air or anoxygen/nitrogen or air/nitrogen mixture (“lean air”). A preferred methodfor the oxidation of the adsorption composition precursor is to stop thehydrogen feed after the reduction, flush the residual hydrogen from thereaction vessel with nitrogen, and then adjust to the desired oxidationtemperature and mix a small proportion of oxygen into the nitrogenstream. Temperature, total gas volume, oxygen content and treatment timemust be optimized by routine experiments with determination of thereduction level for each individual case. A typical suitable gas mixturecomprises for example at least 0.05 vol. % oxygen in nitrogen,preferably at least 0.1 vol. % and particularly preferably at least 0.15vol. % and at most 0.5 vol. %, preferably at most 0.4 vol. % andparticularly preferably at most 0.25 vol. %. A suitable value is forexample 0.2 vol. %. A typical oxidation time is in general at least 24hours, preferably at least 48 hours and particularly preferably at least60 hours and in general at most 100 hours, preferably at most 90 hoursand particularly preferably at most 80 hours. For example, oxidation isperformed for 70 hours. The gas volume to be used is typically at least50 NL gas per liter of adsorption composition precursor and hour(NL=normal liter, i.e. based on 0° C. and normal pressure), preferablyat least 100 NL/l*hrs and particularly preferably at least 150 NL/l*hrsand in general at most 5,000 NL/l*hrs, preferably at most 1,000NL/l*hrs, and particularly preferably at most 500 NL/l*hrs. For example,200 NL/l*hrs is very suitable. The adjusted temperature is in general atleast 30° C., preferably at least 35° C. and particularly preferably 40°C. and in general at most 80° C., preferably at most 70° C. andparticularly preferably at most 60° C. For example 50° C. is verysuitable.

For the use thereof, the adsorption composition shaped bodies are filledinto a vessel described as an “adsorber”, sometimes also “reactor”,wherein they are contacted with the substance stream to be purified.

The finished adsorption composition is preferably dried (if necessaryagain) before its use for the adsorption of CO in order to remove tracesof adhering moisture and to increase the adsorption capacity. The dryingof the finished adsorption composition is performed like the drying ofits precursor described above.

The adjustment of the reduction level and the drying are convenientlyperformed in the adsorber, since otherwise considerable effort isnecessary to protect the ready-for-use activated adsorption compositionfrom air and moisture during filling into the adsorber.

Following the adjustment of the reduction level and a possibly dryingoperation performed before or after the adjustment of the reductionlevel, the adsorption composition according to the invention is readyfor use.

The adsorptive process according to the invention is particularlysuitable for the removal of carbon monoxide from ethene, propene,1-butene, 2-butene, 1,3-butadiene, butene mixtures, butene/butadienemixtures or styrene in order to lower the carbon monoxide content tovalues permissible for “polymer grade” olefins. In a quite especiallypreferred embodiment, carbon monoxide is adsorptively removed fromliquid propene with the process according to the invention.

The adsorptive process according to the invention is particularlysuitable for the removal of carbon monoxide from substance streams whichin general comprise at least 0.001 ppm (for gases vol. ppm, for liquidswt. ppm), preferably at least 0.01 ppm and in general at most 1000 ppm,preferably at most 100 ppm and particularly preferably at most 10 ppm ofcarbon monoxide. For relatively high initial concentrations of carbonmonoxide, it is usually more economical to perform a different knownpurification process such as distillation, catalytic oxidation of thecarbon monoxide with oxygen to carbon dioxide or oxidation of the carbonmonoxide with copper oxide with the formation of metallic copper andcarbon dioxide beforehand, optionally with subsequent separation ofcarbon dioxide and oxygenation products, since otherwise the adsorptioncapacity of the adsorption composition can be reached too quickly.

For implementation of the adsorptive process according to the invention,the substance stream to be freed from carbon monoxide is passed over thebed of the adsorption composition shaped bodies according to theinvention in the adsorber.

From the technical point of view, the temperature is not or not verycritical for the adsorptive process according to the invention. Typicaltemperatures lie in the range from at least −270° C., preferably atleast −100° C. and particularly preferably −40° C. and at most 300° C.,preferably at most 200° C. and particularly preferably at most 100° C.

A significant parameter determining the depletion level is the contacttime between substance stream and adsorption composition. This contacttime is determined by the flow rate of the substance stream and thevolume of the adsorption composition bed. Mostly, the volume flow of thesubstance stream to be purified is predetermined by the capacity ofupstream or downstream units. Advantageously at least two adsorbers areprovided, at least one of which can be exposed to a substance stream tobe purified, while the adsorption composition is regenerated in at leastone other.

Depending on the adsorber size selected, the maximum uptake capacity ofthe adsorption composition comprised therein for carbon monoxide issooner or later reached, so that it must be regenerated.

For the regeneration of the adsorption composition according to theinvention, firstly the substance stream to be purified is stopped, andit is preferably passed into a parallel adsorber filled with fresh orregenerated adsorption composition.

The invention is explained in more detail by the following examples.

Examples

The adsorption performance of an adsorption composition for the removalof CO from a propylene gas flow was systematically studied in a gasphase apparatus. The adsorption composition is the reduced form of anoxide precursor composition consisting of 70 wt. % CuO, 20 wt. % ZnO and10 wt. % ZrO₂. For production of this oxide precursor composition, aCu—Zn—Zr nitrate solution (metal content 15.2 wt. %, Cu:Zn:Zr ratiocorresponding to a CuO:ZnO:ZrO₂ weight ratio of 7:2:1) was precipitatedwith soda solution (20 wt. %) at pH 6.5 and 70° C. After completion ofprecipitation, the suspension was stirred for a further 120 minutes atpH 6.5 and 70° C. Next, the solution was filtered, and the filter cakewashed free of nitrate with demineralized water and dried at 120° C. Thedried powder was calcined at 300° C. for 240 minutes in the forced airoven, then mixed with 3 wt. % graphite and compressed into 3×3 mmtablets with a side pressure of 50 N. The tablets were further calcinedat 425° C. for 120 minutes.

The gas phase apparatus consisted of a reactor equipped with electricaljacket heating. The flow through the reactor was effected from top tobottom. The reactor had an internal diameter of 44.3 mm (DN40) and alength of 168 mm. The reusable thermoelement had an external diameter of3.2 mm and 5 measurement points. The gas supply was provided by means ofnormal commercial mass flow controllers.

The carbon monoxide concentration was measured online via IR absorption.

The test conditions were as follows:

T: room temperature

p: 1 bar

Catalyst volume: 85 ml

Propylene flow: 150 NL×hrs⁻¹

GHSV: 1.765 hrs⁻¹

CO concentration: 100 ppm

The integral CO uptake capacity of the adsorption composition wasdetermined up to the breakthrough of CO, which was assumed to be when 10vol. ppm of CO were measured in the reactor exit gas.

Determination of the CO Uptake Capacity as Function of Reduction Level

The CO uptake capacity of the adsorption composition as a function ofthe reduction level R was determined as follows:

For the determination of the CO uptake capacity as a function of thereduction level, several adsorption compositions with differentreduction levels were specifically prepared and each one tested asdescribed above.

The reduction level of the individual adsorption compositions wasdetermined by the formula stated above.

A marked dependence of the CO uptake capacity on the reduction level ofthe copper was observed. The oxide material with R=0 displayed no COuptake capacity. Up to an R of 2%, the uptake capacity rises rapidly to0.3 NL CO (per liter of adsorption composition), then to fall again to0.05 NL CO between R=2% and R=30%. Above R=30%, the CO uptake capacitythen rises to an overall maximum of 0.8 NL CO. This maximum is reachedat R=85 to 90%. Above R=90%, the CO uptake capacity falls abruptly,until at R=100% the material no longer displays any CO uptake capacity.

FIG. 1 presents the results of the measurements,

Because of the marked dependence of the CO uptake capacity on thereduction level, it is very important that the reduction level remainsessentially constant during operation. A reduction level in the rangefrom 65 to 75% is optimal, since the adsorption composition then alreadydisplays a sufficiently high uptake capacity of 0.4 NL CO, but therestill exists a sufficient distance from the reduction levels whichresult in low uptake capacities.

Further Activation by Regeneration with Pure Inert Gas

As soon as the maximal CO uptake capacity of the adsorption compositionwas reached, a breakthrough of CO was observed. At this time point, thegas feed stream was stopped and the catalyst was heated to 200° C. forthe regeneration. The minimum temperature for effective regeneration was190° C. Below 180° C. no significant regeneration was observed. Theregeneration was effected with industrial nitrogen at 200 to 250° C.

It was shown by IR that during the regeneration it was not CO, but CO₂,which is desorbed from the adsorption composition. In addition, adsorbedpropylene is also oxidized by lattice oxygen atoms during theregeneration, whereby CO₂ is also formed. As a result, in everyregeneration step which is performed with pure nitrogen the catalyst isreduced. The reduction level increases by 1.5 to 2% per regenerationstep.

For example, a freshly prepared catalyst with an initial reduction levelR of 77% displayed an increase in the CO adsorption capacity fromadsorption step to adsorption step through regeneration with N₂.However, after about 7 regenerations, the CO uptake capacity began tofall markedly, since a critical reduction level was then exceeded.

FIG. 2 presents the results of the experiments with an adsorptioncomposition with an initial reduction level of 77%. Between tworegeneration steps an adsorption step was performed each time, and themaximal CO uptake capacity determined.

In the first adsorption step, the freshly prepared adsorptioncomposition in general displayed only a low CO uptake capacity. XPSmeasurements have shown that after the production of the catalyst,adsorption-active Cu(I) on the surface is coated with a thin layer ofCuO and Cu(OH)₂. This layer impedes the adsorption of CO.

In the first regeneration cycle with the use of pure N₂ as theregeneration gas, the CuO and Cu(OH)₂-comprising layer was reduced to alayer of Cu₂O by oxidation of the adsorbed species (CO and propylene).As a result of this, the CO uptake capacity in the second adsorptioncycle increased markedly compared to the first adsorption cycle.

An adsorption composition with a lower initial reduction level R of only67% needed more regeneration cycles, compared with an adsorptioncomposition with an initial reduction level of 77%, until the optimal COuptake capacity was reached.

FIG. 3 presents the results of the regeneration of an adsorptioncomposition with an initial reduction level of 67% with industrialnitrogen at 250° C. Between two regeneration steps an adsorption stepwas performed each time, and the maximal CO uptake capacity determined.

Activation by Treatment with Propylene-Comprising Inert Gas and PureInert Gas (According to the Invention)

An untreated catalyst with a reduction level of 75% displayed a COuptake capacity of only 0.08 NL CO per liter of adsorption compositionin the first cycle. If the same catalyst was first treated for 1 hrs at30° C. with a mixture of 50% propene and 50% N₂ at a GHSV of 1,765hrs⁻¹, and then baked with industrially pure nitrogen at 250° C. for 3hours, the CO uptake capacity increased to 0.55 NL CO per liter ofadsorption composition.

Regeneration with Oxygen-Comprising Inert Gas

After the activation phase in which the regeneration was performed withindustrially pure nitrogen, after each adsorption step the regenerationwas performed with a nitrogen stream which comprises 1500 ppm oxygen.The temperature during this was 200° C. and the GHSV was 500 hrs⁻¹. Overa total period of 3 hours, 2.3 NL of oxygen were fed in per liter ofcatalyst.

FIG. 4 shows the results of experiments in which regeneration steps 1 to4 were performed with pure N₂ at 250° C. and the regeneration steps 5 to9 at 200° C. with nitrogen comprising 1500 ppm O₂. Between each ofthese, an adsorption step was performed and the maximum CO uptakecapacity determined.

As can be seen from FIG. 4, the result of regeneration with theoxygen-comprising regeneration gas was that the CO uptake capacity ofthe adsorption composition remained essentially constant.

The invention claimed is:
 1. A process for the activation of a copper-,zinc- and zirconium oxide-comprising adsorption composition for theadsorptive removal of carbon monoxide from substance streams comprisingcarbon monoxide and at least one olefin, wherein (i) in a firstactivation step an activation gas mixture comprising the olefin and aninert gas is passed through the adsorption composition, and (ii) in asecond activation step the adsorption composition is heated to atemperature in the range from 180 to 300° C. and an inert gas is passedthrough it, wherein the steps (i) and (ii) can each be performed severaltimes.
 2. The process according to claim 1, wherein the adsorptioncomposition comprises copper in a quantity which corresponds to 30 to99.8 wt. % CuO, zinc in a quantity which corresponds to 0.1 to 69.9 wt.% ZnO and zirconium in a quantity which corresponds to 0.1 to 69.9 wt. %ZrO₂, each based on the total quantity of the adsorption composition. 3.The process according to claim 1, wherein the adsorption compositioncomprises copper in a quantity which corresponds to 65 to 75 wt. % CuO,zinc in a quantity which corresponds to 15 to 25 wt. % ZnO and zirconiumin a quantity which corresponds to 5 to 15 wt. % ZrO₂, each based on thetotal quantity of the adsorption composition.
 4. The process accordingto claim 1, wherein the activation gas mixture comprises 1 to 100 vol. %propene in nitrogen.
 5. The process according to claim 1, wherein thecopper-comprising fraction of the adsorption composition before theactivation is performed has a reduction level of less than 65%.
 6. Theprocess according to claim 1, wherein the copper-comprising fraction ofthe adsorption composition after the activation is performed has areduction level of at least 65% and at most 75%.
 7. The processaccording to claim 1, wherein the steps (i) and (ii) are each performed1 to 10 times.